The present invention relates generally to apparatus for controlling the flow of water, and more specifically to a moisture-actuated apparatus responsive to the moisture content of a water-conducting medium for controlling the flow of water in a system or through a device which delivers water to the medium.
As is known, it is required to deliver water to irrigation systems on demand, in response to the moisture content of a medium to be irrigated. Thus, system control is directed to operating the system to irrigate at times when, for example, the medium is relatively dry. Moreover, it is desirable to effect such control without requiring constant human supervision to make and implement the decision to irrigate. Automatic control devices are known which monitor the hydration of irrigated areas and make system control decisions based upon the electrical characteristics of soil, which change with its moisture content. However, such apparatus require the provision of electrical power to perform the monitoring as well as to operate the system. This results in an excessive requirement for electrical power. Further, constant exposure to the hydrated and chemically treated soil which is serviced by the irrigation system can corrode metallic parts which perform the electrical sensing function, thereby resulting in a reduction in the quality of system performance. Finally, the conductivity of soil changes with changing chemical content, which results in a requirement to reset an electrical sensing system whenever soil is chemically treated.
Therefore, in an irrigation system which delivers water to a medium to be irrigated, it would be desirable to provide an apparatus for controlling the flow of water to the system which is responsive to the moisture content of the medium, which is automatically actuated by the moisture content of the medium, yet which depends for its operation on the provision of no electrical power. Further advantage would attend the use of an accurate, long-lasting, troublefree actuator to perform such actuation in response to the presence of absence of water.